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Diverticular Disease of the Colon

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Diverticula are sac-like protrusions of the mucosa and submucosa that bulge through weak spots in the muscularis propria of the colon.

The presence of these sac-like pouches is called diverticulosis.

When these pouches become inflamed or infected, it's called diverticulitis.

The most common site for diverticula formation is the sigmoid colon, which has a relatively small diameter.

According to the Law of Laplace, a smaller diameter results in greater intraluminal pressure, which significantly increases the tension on the colonic wall.

When intraluminal pressure rises due to factors such as straining during bowel movements, chronic constipation, and decreased stool bulk from a low-fiber diet, the mucosa and submucosa are forced outward through the weak points of the bowel wall, forming diverticula.

Over time, the circular muscle layer may thicken, and the longitudinal muscle bands known as the taeniae coli may shorten.

These structural changes are accompanied by increased deposition of collagen and elastin, which stiffen the colon and impair its motility.

As a result, segmentation increases, and local pressure rises further, promoting the formation of additional diverticula.

Overview

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Diverticular disease involves the formation of diverticula—small sac-like outpouchings of the colonic wall—and their complications. It most commonly affects the sigmoid colon due to higher intraluminal pressure and structural vulnerability. It results from structural weakness and increased pressure in the colon, producing pseudodiverticula that may remain silent or progress to inflammation and serious complications.

Structure of Diverticula

In diverticulosis, these outpouchings are pseudodiverticula, involving only mucosa and submucosa that herniate through weak points in the muscular layer, unlike true diverticula, which involve all layers. The colon’s longitudinal muscle is arranged into three bands (taeniae coli). These bands create spaces where blood vessels—specifically the vasa recta—penetrate the circular muscle layer to supply the mucosa. These entry points are structurally weak and prone to herniation when pressure builds up inside the colon.

Pathogenesis

Increased intraluminal pressure—often from chronic constipation, straining, or low-fiber diets—causes mucosal bulging at these weak points. Segmental contractions narrow the lumen, further raising pressure. Diverticula, typically 0.5–1 cm, appear as flask-shaped pouches, often near taeniae coli and distinct from normal haustra (the areas where the colon contracts and bulges).

Clinical Features

Diverticulosis is often asymptomatic and incidentally detected. When stool becomes trapped, bacterial overgrowth leads to diverticulitis, presenting with left lower abdominal pain, fever, nausea, vomiting, and tenderness.

Complications include micro- or macroperforation causing abscesses or peritonitis, and fistulas (e.g., vesicovaginal fistulas) creating an abnormal connection between the colon and bladder—leading to symptoms such as air in the urine (pneumaturia), bowel obstruction from fibrosis, and bleeding due to vessel erosion.

Transcript

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